1. Field of the Invention
This invention relates to servicing a wellbore. More specifically, it relates to servicing a wellbore with cement compositions having a low heat of hydration.
2. Background of the Invention
Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. Subsequent secondary cementing operations may also be performed.
The completion of subterranean wellbores in fragile geographic zones such as in permafrost poses particular challenges. Permafrost is defined as soil that stays in a frozen state for more than two years. Cement compositions for use for in subterranean formations within zones of permafrost must be designed to set before freezing and have a low heat of hydration. In addition to destabilizing the formation, high heats of hydration promote the evolution of gas hydrates (e.g. methane hydrate) that are present in large amounts in permafrost. Gas hydrates, for example methane hydrate, are metastable and can easily dissociate.
Thus there is an ongoing need for cement compositions having a low heat of hydration.